There has been continued development of communication links to interconnect a computer to other computers, peripheral equipment, local area networks, the internet etc. These communication links typically use copper cable, optical fiber, or wireless as the transmission medium. Because of bandwidth, cost, and interference concerns, optical fiber has become one of the preferred mediums of choice. Because of lower connection costs and robustness, multi-mode glass fiber had become more desirable than single mode glass fiber. Illustrative of such multi-mode optical communication links is the lightwave transmission system described in U.S. Pat. No. 5,416,862, issued to Haas et al, on May 16, 1995, and entitled "LIGHTWAVE TRANSMISSION SYSTEM USING SELECTED OPTICAL MODES." Shown in FIG. 1 is an illustrative multi-mode optical fiber system similar to that disclosed in the patent. To increase the capacity of the multi-mode optical fiber system, a single-mode fiber 104 is connected through a coupler 105 to the multi-mode fiber 107. The coupler 105 is used to selectively propagate only higher-order modes over the multi-mode fiber 107. Other arrangements splice the single-mode fiber 104 to the multi-mode fiber 107 to facilitate the launching of only the lower-order modes over the multi-mode fiber 107.
In an effort to further decrease costs, polymer (plastic) optical fiber (hereinafter also referred to as POF) has been developed for use in optical transmission systems. Because of its large diameter polymer fiber also promotes multi-mode transmission. However, because of its relatively high transmission loss characteristics and its less-desirable transmission wavelength, about 650 nm, polymer fiber has typically only been used in short distance applications. Recently, POF have also been proposed for use in optical transmission systems. An illustrative system is described in the article by H. Imai entitled "APPLICATIONS OF PERFLUORINATED POLYMER FIBERS TO OPTICAL TRANSMISSION," published on Sep. 22,1997 in Proceedings of Seventh International Plastics Optical Fiber Conference, pp. 29-30. FIG. 1 is a simplified representation of the PF fiber based optical system described in the Imai article. Again a single-mode fiber 104 is connected in front of the POF 107 and is used to selectively propagate only lower-order mode transmission over the multi-mode POF.
While the above article illustrates that significant improvements have been made in the use of POF in optical transmission systems, there is a continuing need to simplify such systems and to make them more cost effective.